Manual respiration bags are used for the manual positive pressure respiration (ventilation) of patients in the area of intensive care and neonatal intensive care to maintain ventilation. The compression of the manual respiration bag causes an increase in the pressure in the respiration bag and a resulting breathing gas flow in the direction of the patient. The breathing volume thus administered as well as the respiration pressure necessary for this depend on the characteristics of the lungs and the respiratory tract of the particular patient. The manual respiration bags currently in use have as the safety means a pressure relief valve, which opens when a predetermined pressure is reached and this limits the respiration pressure.
The known respiration bags are also used to respirate or ventilate premature babies. It appears from numerous publications that the cause of the overinflation of the lung is not the respiration pressure but the tidal volume administered. A sufficient monitoring system is frequently unavailable to the user in conjunction with the manual respiration precisely for the respiration of premature babies. The pressure relief valve at the manual respiration bag also limits only the maximum pressure, but it does not control the tidal volume.
A respirator for the controlled mechanical respiration of patients, in which a volume-measuring means is provided between a respiration bag and a patient connection, is known from DE 195 28 113 C2. The prior-art respirator is used to recognize respiratory tract obstructions. Time constants of sections of the function are calculated and evaluated for this purpose in an evaluating means from an expiratory volume-flow function. However, the prior-art respirator contains no means for limiting the tidal volume supplied to the patient.